How to get the process ID to kill a nohup process?

When using nohup, it will give you the PID at the command prompt. If your plan is to manually manage the process, you can save that PID and use it later to kill the process if needed, via kill PID or kill -9 PID (if you need to force kill). Alternatively, you can find the PID later on by ps -ef output | grep "command name" and locate the PID from there. Note that nohup does not appear in the ps output.

If you used a script, you could do something like:

nohup my_command > my.log 2>&1&
echo $! > save_pid.txt

This will run my_command saving all output into my.log (in a script, $! represents the PID of the last process executed). If the command sends output on a regular basis, you can check the output occasionally with tail my.log, or if you want to follow it "live" you can use tail -f my.log. Finally, if you need to kill the process, you can do it via:

kill -9 `cat save_pid.txt`